[6] After returning from his loan spell at Odra Opole, Moder extended his contract with Lech Poznań until 2023,[7] and quickly became a regular starter under Dariusz Żuraw.

Moder made his debut for Brighton on 10 February 2021, starting and playing the full match in the 1–0 away defeat against Leicester City in the FA Cup fifth round.

[16] He made his Premier League debut on 27 February coming on as a substitute for Ben White in the 84th minute in a 1–0 away loss at West Bromwich Albion.

[19] Moder set up Albion's equaliser with his ball into the box met by a sliding Neal Maupay with Alexis Mac Allister scoring the winner five minutes later in the 2–1 away victory over Burnley on 14 August in the opening game of the 2021–22 season.

[22] On 2 April, during the 0–0 home draw against Norwich City, Moder landed awkwardly which resulted in an injury to his anterior cruciate ligament (ACL)].

[31] on 11 November 2020, he scored his first goal for the national team just seconds after coming on as a substitute for Arkadiusz Milik, as Poland defeated Ukraine 2–0 in a friendly match.

[32] He scored his second goal for his country capitalising on a John Stones mistake in a 2–1 away loss against England on 31 March 2021 in a 2022 World Cup qualifier.

[33] Moder was named in Poland's 26-man squad for Euro 2020 on 17 May 2021, with the tournament taken place in the summer of 2021 due to the previous year's postponement as a result of Coronavirus.